Tsuneyuki Oikawa

XENOGENIZATION OF TUMOR CELLS BY TRANSFECTION WITH PLASMID CONTAINING env GENE OF FRIEND LEUKEMIA VIRUS

A rat hepatocellular carcinoma cell line (cKDH‐8 cl‐11) showed decreased tumorigenicity after transfection with an envelope gene derived from a Friend leukemia virus (FV‐env gene). FV‐env gene product was found by indirect immunofluorescence staining to be expressed on the cell surface of the FV‐env gene‐transfected cells. The FV‐env‐transfected cells (FV‐env cKDH‐8), however, grew well in X‐irradiated immunosuppressed rats, indicating that the reduction in tumorigenicity of the transfected cells is based on immunological reaction in the host. The rats which rejected FV‐env cKDH‐8 cells showed resistance to rechallenge with the parent cKDH‐8 cl‐11 tumor cells. These results suggest that the FV‐env gene product may elicit antitumor immunity against FV‐env cKDH‐8 cells in a host with a resultant reduction in the tumorigenicity of these cells.

Chromosome and cell surface marker studies in 1-propyl-1-nitrosourea-induced thymic lymphomas of the rat

Immunological cell surface markers were studied in seven transplantable 1-propyl-1-nitrosourea-induced thymic lymphoma lines in F344 rats by reactivity to anti-Thy-1.1, anti-rat Ig (anti-Ig), and anti-rat T-cell (anti-T) sera, and by the capacity to form rosettes with guinea pig red blood cells. All the tumor lines were estimated to be sensitive to anti-Thy-1.1 but insensitive to anti-Ig serum in the presence of complement. The differences in reactivity to anti-T serum and rosette-forming capacity (RFC) allowed classification of the lines into three types. In type I, three lines were highly sensitive to anti-T serum but low in RFC, indicating that these lymphomas probably originated from relatively mature intrathymic T cells. In type II, two lines were moderately sensitive to anti-T serum and relatively high in RFC, indicating that these lymphomas derived from intrathymic T cells. In type III lymphomas, the remaining two lines were not only insensitive to anti-T serum but also low in RFC, suggesting that these lymphomas might have arisen from immature precursors of T and/or B cells. The chromosome study revealed that type I lymphomas were diploid, with slight numerical and structural variations. Type II lymphomas were pseudodiploid or hypotetraploid, with considerable variation in the number and morphology of chromosomes. Type III lymphomas had a diploid or hyperdiploid constitution, with a moderate degree of karyotypic variation. Neither consistent nor common karyotypic alterations among the seven lines were found, although the karyotypic instability seemed to be related to the immunological types of the lymphoma lines, possibly reflecting the differentiation process of the target cells involved in the malignant transformation.

Reduced DNase I sensitivity of the rearranged c-myc gene in somatic cell hybrids between murine plasmacytoma cells and fibroblasts☆

In mouse plasmacytoma (MPC) S194, the rearranged c-myc gene was much more sensitive to DNase I digestion than the nonrearranged gene. The sensitivity of the rearranged c-myc was markedly reduced to the same extent as that of the nonrearranged one in hybrids between the MPC cells and the fibroblasts, but not in a hybrid between the MPC and the spleen cells. These results suggest that trans-acting factors in fibroblasts alter the DNase I-sensitive structure of the rearranged c-myc gene.

Unresponsiveness of both non-rearranged and rearranged c-myc to serum stimulation in a mouse plasmacytoma S194

Expression of non-rearranged and rearranged c-myc in a mouse plasmacytoma cell line S194 cultured in different serum concentration or temperature was examined. Exponentially growing S194 cells expressed a high level of rearranged c-myc and a low level of non-rearranged c-myc mRNAs. The levels of the two c-myc mRNAs were nearly the same in the cells in which growth was suppressed by lowering serum concentrations or incubation temperature in culture medium. Furthermore, even when serum-deprived S194 cells resumed growth following serum restimulation, the induction of non-rearranged c-myc mRNA, observed in a mouse T-cell lymphoma cell line BW5147, was not demonstrated. In contrast to the unchanged c-myc expression, the level of N-ras mRNA was related to changes in cell growth rate induced by changes in serum concentration in S194 cells. These results suggest that not only the rearranged c-myc but also the non-rearranged c-myc is unresponsive to serum stimulation and temperature changes, even though cell growth rate is markedly changed.

Immunological regression of metastatic cancer in the liver as a result of "in vivo xenogenization"

We attempted to induce the regression of liver metastatic tumor cellsin vivo by the administration to rats of Friend leukemia virus (FV) (in vivo xenogenization). The virus which was used in this experiment, FV, is highly immunogenic and does not normally cause disease in an adult rat. At first, we induced a FV viremia in tumor bearing rats in order to deliver the virus to the site of the tumor cells. FV viremia was induced by injecting 60 mg/kg cyclophosphamide (CY) i.v. after the administration of FV, and by transferring syngeneic bone marrow cells so that FV would be able to infect them and then replicate.In order that the tumor cells which were infected with virus should regress, it was necessary to break down their tolerance to FV antigens. As adoptive immunotherapy we therefore, transferred syngeneic spleen cells from rats which had been immunized with FV to tumor bearing rats. The result of this experiment was that these tumor bearing rats infected with FV which had received either normal syngeneic spleen cells or no spleen cells as controls died from liver metastasis (8 out of 9 rats (89%) and 15 out of 17 (88%) respectively). On the other hand, only 4 out of the 15 (27%) tumor bearing rats which were infected with FV and which received FV-immune spleen cells died from liver metastasis.These sets of data indicate that thein vivo xenogenization of tumor cells are indeed able to induce the regression of metastic tumor cells.